Raman scattering investigation of large positive magnetoresistance material WTe$_2$

TL;DR

This study uses polarized Raman scattering to analyze phonon modes in WTe$_2$, a material with large positive magnetoresistance, revealing specific phonon behaviors and their temperature dependence.

Contribution

It provides detailed Raman spectra of WTe$_2$ and insights into phonon behavior, with first-principles calculations supporting experimental observations.

Findings

Identified 5 A$_1$ and 2 A$_2$ phonon modes in WTe$_2$

Observed temperature-dependent intensity change in a specific A$_1$ phonon mode

Phonon spectra suggest weak electron-phonon coupling

Abstract

We have performed polarized Raman scattering measurements on WTe$_2$, for which an extremely large positive magnetoresistance has been reported recently. We observe 5 A$_1$ phonon modes and 2 A$_2$ phonon modes out of 33 Raman active modes, with frequencies in good accordance with first-principles calculations. The angular dependence of the intensity of the peaks observed is consistent with the Raman tensors of the $C_{2v}$ point group symmetry attributed to WTe$_2$. Although the phonon spectra suggest neither strong electron-phonon nor spin-phonon coupling, the intensity of the A$_1$ phonon mode at 160.6 cm$^{-1}$ shows an unconventional decrease with temperature decreasing, for which the origin remains unclear.